Australia's conservative opposition leader, Tony Abbott, has vowed to make trustworthiness in a prime minister the core issue in the 14 September election that has been unexpectedly announced eight months in advance by Julia Gillard.

In a development that may raise questions about political timing, an ex-MP of Gillard's Labor party, Craig Thomson, was arrested on fraud charges as Abbott was giving his speech to the National Press Club.

Thomson was forced to step down from the party in 2012 while facing allegations of fraud, including the procurement of prostitutes on union credit cards when he was a senior figure in the Health Services Union between 2002 and 2007.

One of Abbott's key themes throughout his time as opposition leader has been to question the prime minister's judgment, particularly over her initial support for Thomson. The arrest on Thursday provided Abbott with another opportunity to attack Gillard on this point and he wasted no time – he said the charges against Craig Thomson went well beyond what he "may or may not have done".

"It's always been about the judgment of the prime minster who [by letting him remain as a Labor MP until last year] was running a protection racket for Craig Thomson for months or years," Abbott said.

A police statement said a further 149 fraud charges would be laid against Thomson. His lawyers said he would plead not guilty in an initial court appearance expected to take part next week.

Thomson has previously strenuously denied allegations he misused union funds to pay for prostitutes, air travel, entertainment and made cash withdrawals when he was the union's national secretary.

Gillard, the prime minister, broke the surprise early news of an election at the National Press Club on Wednesday, and in his reply speech on Thursday at the same venue Abbott set out the big themes of the campaign he intended to run. Top of the list was trust.

"Before the [2010] election the government promised that it would be delivering a budget surplus but no carbon tax. In fact it's delivered a carbon tax but no budget surplus," he said.

"So my pledge to you is I won't say one thing to you before the election and do the opposite afterwards because fibbing your way into office is what's brought our public life into disrepute."

If Australians had any faint hope that Gillard's announcement had launched anything other than what the prime minister herself described as "the nation's longest ever election campaign", they would have been sorely disappointed by Abbott's reply speech in which he targeted her with a list of grievances.

Abbott's delivery was noticeably more softly spoken than usual, though – an attempt to take the edge off his reputation as an aggressive attack-dog campaigner. A strong economy, border security and the abolition of the carbon tax on high greenhouse gas emitting businesses were key themes.

"You want less pressure on your cost of living, you want more job security, you want our border under control and you want a leader you can trust," he said.

During the speech Abbott also aired his credentials as a family man. "I want the best possible life for my three daughters as we all do for our children. I want it to be easier for them than it was for [my wife] Margie to have a family and keep a career," he said.

The prime minister has no children and Abbott has been criticised for snide remarks about this. Gillard famously denounced Abbott as a misogynist in a fiery speech to parliament

Speaking in the Queensland town of Bundaberg, which has been devastated by recent flooding, the prime minister, Gillard said she had only just heard about the media reports concerning Thomson's arrest.

She denied having any prior knowledge of the impending arrest before announcing the election date on Monday. "Of course not," she said.

When asked to comment on Tony Abbott's assertion that Thomson's situation was about the prime minister's judgment she responded: "I'm not going to engage in any of that sort of argy bargy today."

Recent polls suggest Abbott's conservative opposition is marginally ahead. A Newspoll carried out by the Australian newspaper put his Liberal-National coalition in front of Labor by 51% to 49%. Despite this Abbott's personal rating remains much lower than the prime minister's.

Sign up for the Guardian Today

Our editors' picks for the day's top news and commentary delivered to your inbox each morning.

About this article

This article was published on
the Guardian website
at 00.23 EST on Thursday 31 January 2013.
It was last modified at 10.27 EST on Tuesday 6 January 2015.
It was first published at 22.40 EST on Wednesday 30 January 2013.